Lightning is a terrifying yet majestic force of nature, especially when you see it from an airplane. But scientists have recently discovered that lightning can sometimes be invisible—and it could be bombarding planes with radiation as they fly.

Dark lightning appears sometimes to compete with normal lightning as a way for thunderstorms to vent the electrical energy that gets pent up inside their roiling interiors, Dwyer says. Unlike with regular lightning, though, people struck by dark lightning, most likely while flying in an airplane, would not get hurt. But according to Dwyer's calculations, they might receive in an instant the maximum safe lifetime dose of ionizing radiation - the kind that wreaks the most havoc on the human body.

Turns out the only real way to tell if a plane has been hit by dark lightning is to use a radiation detector. But the good news is that dark lighting is, apparently, mercifully rare, occurring just once for every 1,000 visible strikes. Combine that with the fact that pilots tend to try and avoid serious storms, and things are looking fairly safe. Phew. [Washington Post]